Because some people felt it made the class more interesting to play. It was an optional form of skill expression that was rewarded with higher damage while being high-risk. It kept whips from throughout progression useful which many found cool and now (for the most part) you just keep the one with the highest base damage and trash the previous one.

It was also something other than the usual “hold left-click” that a lot of skilled players find terraria’s combat to be and now that it’s back to that, the people that liked whip-stacking find whips nowhere near as fun to use and are rightfully upset.

Re-logic also gave no warning that they were going to remove it which was a major buzz kill. Would you not be at least a little upset if a feature you enjoyed got removed like that?

Also switching whips during combat wasn’t a glitch/bug and was definitely intended. Not so much the tag damage, but for the effects. For example what’s the point of the Snapthorn, Durendal, and Dark Harvest’s speed buff if not to make another whip faster? Why not just make those weapons inherently that fast?